That too, actually, or "almost." In our case, in 1999 or so, we had to develop an actively redundant link layer protocol, for high speed, high survivability networks. Lo and behold, in 2010, IEC 62439-3 is created: Parallel Redundancy Protocol. It's not identical to ours, and I much prefer our approach for a couple of reasons (nothing like developing your own to understand the advantages and disadvantages of other approaches you had to explore in the process), however overall, the way it works is the same. The differences are in flexibility of the link layer topology and in maximum speed the protocol can support.

The fun part of the job is to keep track of the ongoing standards efforts, and then adopt (and adapt) the successful ones when it makes sense to do so, while still retaining compatibility

the thought occurs to me that on rare occasions this goes the other way, when a proprietary bus is standardised. I'll bet every standard of early serial bus started that way. GIven the structure of Modbus, you can just feel the evolution from a single purpose idea into the general purpose standard.

Absolutely! This topic of rolling your own, vs. using an existing standard, came up in a recent article by Junko Yoshida as well.

We very much created our own protocols, and entire digital networks, before standard ones were good enough to do what we were building. The fun part of the job is to keep track of the ongoing standards efforts, and then adopt (and adapt) the successful ones when it makes sense to do so, while still retaining compatibility with the proprietary protocols that came before.

Ultimately, for our work, adopting standards allows you to improve the products more rapidly. Because you're leveraging off the work of thousands of smart designers all over the world. However that wasn't the situation at the beginning. For my work, this has been true for protocols and also for hardware.